All B and D series clutch slave cylinders are the same. I have compaired my D16y5 one to my B18b1 slave cylinder and they are the same, even both have 3/4 cast into the front. However the clutch line are very different from the B and D engines. If doing a B series swap use the D16's clutch slave and lines, you may need to bend the lines just a bit for fitment.

So why do you say to use the d series? I had my LS with Ls slave on the trans for 10yrs with no problems. I have this high pitch sound when at idle. If I push the clutch in an inch...it goes away. I need to get a long piece of metal (Like a long a$$ screwdriver) and use it to hear if the slace is making that aweful noise. i just wanted to know if I could use the LS slave but now 'intenseneal' says use a d-series??? So no checking with the LS slave?